It's letter C. When ever you read "breaks down" always think decomposition. When you read that compound get together to form "a single" compound, think synthesis.
Answer: 66
Explanation: To find the mass number you would have to add the number of protons and the number of neutrons.
<span>The metalloids; boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), polonium (Po) and astatine (At) are the elements found along the step like line between metals and non-metals of the periodic table.</span>
It is false, the atomic number is the number of protons and/or electrons in an atom on an element.